Identification key for adults of the Bothynus villiersi species group

1 Apex of the prosternal process conical in both sexes (Fig. 4C). If described, female with anterior pronotal border arched (Fig. 8A)................................................................................................ 2

- Apex of the prosternal process rounded in both sexes (Fig. 4D). Anterior pronotal border of female sinuous (Fig. 8B)......................................................... Bothynus belemensis Duarte, Grossi, & Dupuis, new species

2 Pronotal tubercle of male subtrapezoidal (truncate or bilobed at apex) (Fig. 4A). Tergite 8 of female with weakly produced internal plate (Fig. 8E)................................................... Bothynus alvarengai Martínez, 1983

- Pronotal tubercle of male conical (rounded at apex) (Fig. 4B). Tergite 8 of female with strongly produced internal plate (Fig. 8C–D).............................................................................................. 3

3 Inner margin of the right paramere bearing a basal process (Fig. 6D). Tergite 8 of female with bilobed internal plate (Fig. 8D)........................................................................ Bothynus horridus Endrödi, 1968

- Inner margin of the right paramere bearing a medial process (Fig. 6B, H). Tergite 8 of female parabolic (Fig. 8C)......... 4

4 Apex of parameres elongate (Fig. 6B). Tergite 8 of female with a longitudinal sulcus at the internal plate (Fig. 8C)................................................................................. Bothynus villiersi Endrödi, 1968

- Apex of parameres shortened (Fig. 6H). Female unknow.............. Bothynus spinophallicus (Ratcliffe & Cave, 2021)